Circuit breaker with means for facilitating adjustment thereof



Sept. 16, 1969 Q LZH ETAL 3,467,933

CIRCUIT BREAKER WITH MEANS FOR FACILITATING ADJUSTMENT THEREOF Filed Nov, 29, 1966 INVENTORS Francis L. Gelzheiser and Charles E.

WITNESSES Nystrom ATTORNEY United States Patent U.S. Cl. 33784 3 Claims ABSTRACT OF THE DISCLOSURE A, circuit breaker comprises an insulating housing formed to provide an adjustable-tool passage that is blocked by a break-off portion of the housing, which portion can be broken otf to open the passage in order to facilitate adjustment of the circuit breaker trip device.

Certain types of circuit breakers are constructed such that the mechanisms are first calibrated and then completely enclosed by housing parts that are riveted or otherwise fixedly secured together. When one of these breakers falls out of calibration, it i necessary to remove the rivets or other securing means; take the housing parts apart; recalibrate the mechanism; and then secure the housing parts back together. Because this is time consuming and because the operation of removing the rivets or other securing means can cause distortion or breaking of parts, it is relatively expensive to re-calibrate these breakers.

Accordingly, it is an object of this invention to provide an improved circuit breaker with improved means permitting re-calibration of the breaker after the circuit breaker has been completely assembled.

Another object of this invention is to provide an improved circuit breaker of the type comprising a trip device that is fixedly secured to a stationary support, which breaker comprises improved means for permitting recalibration of the breaker after the breaker is completely assembled.

Another object of this invention is to provide an improved circuit breaker of the type that calibrated without an adjusting screw, which breaker comprises means permitting re-calibration of the breaker after the breaker is completely assembled.

Another object of this invention is to provide an improved circuit breaker that is relatively inexpensive to manufacture.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description when taken in conjunction with the accompanying drawings.

In said drawings:

FIGURE 1 is an end view of a duplex-type circuit breaker embodying the principal features of this invention;

FIG. 2 is a sectional view taken along the line III1 of FIG. 1;

FIG. 3 is a view illustrating part of the breaker disclosed in FIG. 2 with a part of the break-off tool illustrated in two positions;

FIG. 4 is a partial view of the breaker seen in FIG. 2 with a calibrating tool in position to re-calibrate the breaker;

FIG. 5 is a sectional view taken generally along the line VV of FIG. 4; and

FIG. 6 is a partial view illustrating part of the breaker seen in FIGS. 2-4 with sealing means applied to close off the passage through which the tool of FIGS. 4 and 5 extends.

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Referring to FIG. 1 of the drawings, a duplex-type circuit breaker 9 is shown therein comprising an insulating housing that comprises insulating parts 11 and 13 forming two compartments. Each of the housing compartment parts 11 and 13 comprise a back portion molded integral with four sides forming an open front. The open front of the part 11 is covered by the back portion of the part 13 and the open front of the part 13 is covered by an insulating cover 15. The three parts 11, 13 and 15 of the housing are held rigidly together by three rivets 16 (FIG. 2) that extend through three openings in each of the three housing parts 11, 13, 15.

The housing compartment parts 11 and 13 form two independent compartments housing two circuit breaker mechanisms which, except for a line terminal structure that will be hereinafter described, are of identical construction and operation, each operating independently of the other. For this reason, only the mechanism enclosed by the housing part 13 will be specifically described, it being understood that unless otherwise mentioned, the description applies to both mechanisms of the duplex circuit breaker.

Referring to FIG. 2 of the drawings, the circuit breaker mechanism that is enclosed by the housing part 13 comprises a stationary contact 21, a cooperative movable contact 23, a supporting metal frame 25, an operating mechanism 27 and a trip device 29.

The operating mechanism 27 is of the type more specifically described in the patent to F. L. Gelzheiser et al. Patent No. 3,213,241, patented Oct. 19, 1965 and assigned to the assignee of the subject case. The trip device 29 is of the type more specifically described in the patent to E. Bullis, Jr., Patent No. 3,200,217, issued Aug. 10, 1965 and assigned to the assignee of the subject case. Thus, only a brief description of the operation mechanism 27 and trip device 29 is given herein.

Two symmetrically constructed clip-on type conducting members 17 -(only one of which is seen in FIG. 2) of resilient conducting material are provided for clipping onto a conducting tab in a load center or panelboard to support the circuit breaker and to electrically connect the two circuit breaker mechanisms to a power source. In each of the compartments, a stationary conductor 21 is welded or otherwise fixedly secured to the associated terminal member 17.

Referring to FIG. 2, the stationary contact 21 cooperates with a movable contact 23 that is welded or otherwise fixedly secured to a small flange of a flat metallic conducting generally C-shaped contact arm or switch arm 41. The contact arm 41 is operated to opened and closed positions by means of an insulating operating member indicated generally at 43, which operating member has a V-shaped opening 45 therein for receiving a projection 47 of the metallic frame 25. The operating member 43 is biased outwardly or upwards as seen in FIG. 2, by means to be hereinafter described, to a position wherein the lower edges of the projection 47 pivotally engage the side walls of the V-shaped opening 45. The switch arm 41 is bent over at its upper end 48 and the bottom portion 49 of the operating member pivotally engages the part 48. The operating member 43 has a handle portion 59 molded integral therewith which extends through an opening in the front of the associated housing part 13 for manual operation. The operating member 43 is provided with arcuate surfaces on opposite sides of the handle 59 to substantially close the housing opening in all positions of the operating member 43.

The frame 25 support-s an insulating pivot 65. A metallic trip member 79 is pivotally supported at one end 7'7 on the insulating pivot support 65. The other end 82 of the trip member 79 has a latch point 83 which rests on a ledge on an armature 86, in an opening in the armature,

to support the trip member 79 in the latched position seen in FIG. 2. The armature 86 is part of the trip device 29 which will be hereinafter described. An overcenter spring 88 is connected, under tension, at the lower end in a slot in the contact arm 41 and at the upper end in a slot in a projection 93 that extends from the trip member 79.

The spring 88 biases the contact arm 41 upward into engagement with the part 49 of the operating member 43 to bias the operating member 43 upward whereby the operating member is biased against the lower edges of the projection 47 of the frame 25.

The movable contact arm 41 is connected by means of a flexible conductor 95 to the lower end of a bimetal 97 which is welded or otherwise fixedly attached near its upper end to a bent-over projection 98 of the metallic frame 25. A load terminal conductor 99 is secured at one end thereof to the upper end of the bimetal 97 and at the other end to a load terminal 100. The terminal 100 is provided with a screw 101 for connecting a conducting line to the terminal 100.

The closed electrical circuit through the breaker extends from the line terminal 17 through the stationary and movable contacts 21, 23, the contact arm 41, the flexible conductor 95, the bimetal member 97, the load terminal conductor 99, to the load terminal 100. Since the movable contact arm 41 extends downward from its pivot, the arc is established adjacent the bottom of the housing, and are chute gases pass out through a vent passage 111.

The circuit breaker may be manually operated to open and close the contacts by operation of the insulating handle 59. Movement of the handle 59 clockwise from the on" position to the o position carries the upper end 48 of the movable contact arm 41 to the left of the line of action of the spring 88 whereupon the spring acts to move the contact arm 41 to the open position shown in broken lines in FIG. 2. A projection 109 molded integral with the housing part 13 acts as a limit stop for the movable contact arm 41 during opening operations. Movement of the operating handle 59 from the off to the on position in a counterclockwise direction moves the upper end 48 of the contact arm 41 to the right of the line of action of the spring 88 whereupon the spring acts to move the contact arm 41 to the closed position.

The trip means 29 is provided for efiecting automatic opening of the circuit breaker upon the occurrence of overloads. The trip device 29 comprises the armature 86, the bimetal 87, a U-shaped magnet member 117 and a spring 119. As was previously set forth, the bimetal 97 is welded or otherwise fixedly secured near its upper end to a bent-over projection 98 of the metal frame 25. The armature 86 is movably mounted on the lower end of the bimetal 97 by means of the spring 119 which is fixedly secured at one end thereof to the armature 86 and at the other end thereof to the lower end of the bimetal 97. The U-shaped magnet member 117 is welded or otherwise fixedly secured to the bimetal 97 with the opposite legs of the U-shaped member extending on opposite sides of the bimetal 97.

Upon the occurrence of an overload current below a predetermined value, the bimetal member 97 becomes heated, and when it is heated a predetermined amount, it deflects to the right as seen in FIG. 2 to effect a time delayed thermal tripping operation. The armature 86, which is supported on the bimetal 97 by means of the spring 119, is carried to the right with the bimetal to release the trip member 79. When the trip member 79 is released, the spring 88 acts to rotate the trip member clockwise about the pivot 65 until this motion is arrested when the trip member 79 strikes the projection 109 of the housing part 13. During this movement, the spring 88 is moved to actuate the contact arm 41 and the operating member 43 to the tripped position in a well known manner. The move ments of the trip member 79 and contact arm 41 are arrested by the projection 109. In order to provide a visual indication that the breaker has been automatically tripped latch the mechanism. This is accomplished by moving the operating handle 59 clockwise from the tripped intermediate position to the full oil position. During this movement, a lower projection 127 on the operating member 43 engages the projection 93 of the trip member 79 to move the trip member 79 counterclockwise until the latch point 83 is again supported in the latched position on the ledge of the armature 86.

The circuit breaker is magnetically tripped automatically and instantaneously in response to overload currents above the predetermined value. Upon the flow of current through the bimetal 97, a magnetic flux, which is induced around the bimetal, takes the path of least reluctance through the magnet member 117, across an air gap 129, and through the armature 86. When an overload current above the predetermined value occurs, the pull of the magnetic flux is of such strentgh that the armature 86 is attracted to the magnet member 117 whereupon the spring 119 flexes permitting the armature to move laterally as well as pivotally toward the member 117. This movement releases the trip member 79, and the contacts are opened in the same manner as was hereinbefore described with respect to the thermal tripping operation.

To calibrate the circuit breaker during the assembly of the breaker, the housing part (11 or 13), frame 25 and the mechanism supported thereby are mounted in a nesting fixture, and a circuit, having a predetermined amount of current, is established through the circuit breaker mechanism. A tool is then worked in an opening 141 in the metal frame 25 to enlarge the opening 141 and move the bimetal 97 and armature 86 to the right until the breaker trips. Two calibrated circuit breaker mechanisms and housing compartment parts 11 and 13 are assembled and the housing parts 11, 13 and 15 are riveted together by means of three rivets 16 to complete the assembly of the circuit breaker.

The circuit breaker is constructed so that the predetermined amount of magnetic air gap 129 will be constant under normal current conditions. As seen in FIG. 1, the bimetal 97 is supported near the upper end thereof on the frame bent-over projection 98. The unrestrained position of the lower or free end of the bimetal 97 is farther to the left than the position in which it appears in FIG. 2, and the bimetal is being stressed slightly to the right by the engagement of a projection 131 on the bimetal 97 with a stop portion 133 on the trip member 79. The bimetal does not deflect when heated by an overload current until this stress is relieved. It can be understood that under normal curren conditions the relative latched positions of the trip member 79 and the bimetal 97 will always be the same. The armature 86 is biased to the left by the spring 119 to a constant position where the armature 86 engages a stop portion 135 on the trip member 79. Because the relative positions of the trip member 79, and bimetal 97 are constant under normal current conditions and because the relative positions of the trip member 79 and armature 86 are constant under normal current conditions, the air gap 129 between the armature 86 and the magnet member 117 must be constant under normal current conditions. This positive positioning provides that the amount of latching engagement between the latched point 83 of the trip member 79 and the latching surface of the armature 86 will also be constant under normal current conditions.

The stop portions 133 and 135 on the trip member 79 are formed from positive die cuts which will remain constant during the life of the die. By controlling the air gap 129 with stop portions 133 and 135, therefore, circuit breakers can be produced in quantity with each breaker having the predetermined amount of magnetic air gap 129.

The air gap 129 is small in dimension so that the breaker will trip open magnetically upon the occurrence of relatively low overload currents without requiring the use of an expensive coil or relatively large iron mass magnetic core member 117. The bimetal 97 is stressed against the stop 133 not only to provide a definite positioning of the parts; but also to enable the construction of the trip device with a small air gap 129 and still permit calibration of the trip device during assembly of the breaker. If the bimetal 97 were not stressed, in some instances, a circuit breaker with a magnetic air gap small enough to permit the required low magnetic tripping could not be properly calibrated for thermal tripping. This problem can be understood from the following hypothetical case:

Assume that FIG. 2 represents, for example, a 15 ampere circuit breaker and that the bimetal 97 is not stressed in the latched position. For the desired low magnetic tripping it is required that the air gap 129 be no more than a certain amount, for example, 0.2 of an inch. For proper thermal calibration, it is necessary that the amount of bimetal deflection necessary for a thermal tripping operation be a certain minimum, for example, a dimension slightly more than .03 of an inch. If the bimetal 97 must move the armature 86 slightly more than .03 of an inch in order to release the'trip member 79, then the amount of latch engagement between the latch point 83 on the trip member 79 and the latch surface on the armature 86 must be at least .03 of an inch, and the armature 86 must move at least .03 of an inch during a magnetic tripping operation in order to release the trip member 79. It can be understood that if the magnetic air gap 129 is a maximum of .02 of an inch, the armature 86 cannot move the necessary .03 of an inch for a magnetic tripping operation. As was previously explained, however, the unrestrained position of the lower or free end of the bimetal 97 is in fact further to the left than the position in which it is shown in FIG. 2 and it is being stressed slightly to the right when the parts are in the latched position. When the bimetal 97 is heated by an overload current, this stress is first relieved before the bimetal starts to deflect in a tripping direction. The bimetal is so stressed in a cold position that the total amount of thermal reaction necessary to move the bimetal, for example, .02 of an inch in order to thermally trip the breaker is at least equivalent to the minimum total amount of thermal reaction that would deflect the bimetal for example, .03 of an inch if it were not stressed in a cold position. Thus, in the trip device with the stressed bimetal there is enough bimetal thermal reaction during a thermal tripping operation to enable accurate thermal calibration and the magnetic air gap 129 is small enough to enable magnetic tripping upon the occurrence of relatively low overload currents.

The housing part 13 is molded to form an elongated passage 145 that is opposite the magnet member 117 at the inner end thereof and that leads out toward the load end of the circuit breaker. The passage 145 is closed or blocked off at the load end by means of an insulating break-off blocking part 147 that is molded integral with the housing part 13. A bottom opening 149 is provided in back of the break-off part 147 leading up toward a slot portion 151 for a reason to be hereinafter described. As can be seen in FIGS. 1 and 2, the break-off part 147 covers or blocks the end opening of the passage 145 when the break-oft part is in position. The breakoff part 147 is molded integral with the housing compartment part 13.

As was previously set forth, the circuit breaker mechanisms are first calibrated, and thereafter the housing parts are riveted together. When the completely assembled circuit breakers are tested, it is found that a small percentage of these breakers are out of calibration. These breakers are out of calibration because they were calibrated improperly or because they fall out of calibration during the assembly and riveting operations. In the past, these breakers were re-calibrated at the plant by the operations of: removing the rivets; taking the housing parts 11, 13, 15 apart; re-calibrating; reassembling the housing parts 11, 13, 15; re-riveting the housing parts together; and finally testing the breakers. This method of re-calibrating this type of circuit breaker is expensive and it occasionally causes breakage and excess distortion of parts. With the provision of the passage 145, when it is i found that a completely assembled circuit breaker has fallen out of calibration, the circuit breaker can be recalibrated without removing the rivets and disassembling the housing. As can be seen in FIG. 3, a rigid break-off tool 155 can be passed up through the opening 149 and positioned in the slot 151. Thereafter, the tool 155 can be levered from the position in which it is seen in full lines in FIG. 3 to the position in which it is seen in broken lines to break off the break-off part 147 of the housing part 13. This operation opens the passage so that an adjusting or calibrating tool 157 can be inserted into the housing through the passage 145 in order to re-calibrate the circuit breaker. The adjusting or calibrating tool 157 is provided with a small hook-part at the working end thereof. If the circuit breaker is found to be out of calibration such that the breaker takes a longer time to trip than is permissible according to certain required standards, the tool is passed into the housing through the passage 145 and hooked around one leg of the magnet member 117. An opening could be provided in the magnet 117, and the tool could be passed through the opening and hooked onto a part of the magnet. The tool 157 is then pulled with a predetermined amount of tension to slightly distort and set the projection 98 (FIG. 2) of the frame 25 to thereby provide less stress of the bimetal 97 against the trip member 79 in the initial position of the circuit breaker. In this case, less thermal reaction will be necessary to move the bimetal in order to effect to a tripping position. The construction and composition of the metal frame 25 and projection 98 are such relative to the construction and composition of the bimetal 97 that when a pulling or pushing force is applied to the bimetal, with the tool 157, the projection 98 will distort, with a twisting action, and take a permanent set to thereby reposition the bimetal 97 relative to the trip member 79. In order to provide uniformity, a spring scale can be added to the external pulled end of the tool 157 to thereby provide a predetermined amount of tension that will provide a slight distortion of the projection 98 to reposition the bimetal 97. This recalibration of the circuit breaker in order to shorten the tripping time is usually effected with the circuit breaker in the tripped position. After the circuit breaker is re-calibrated, the circuit breaker is re-set and a tripping current is then passed through the circuit breaker in order to test the breaker to determine Whether the breaker tripping time is in accordance With the desired standards. If the circuit breaker does not trip in accordance with the desired standards, the tool 157 is again used to re calibrate the circuit breaker. After the breaker has been re-calibrated to the extent that it trips according to the desired standards, the circuit passage 145 is sealed with a suitable cement 161 (FIG. 6). The cement is placed in position as a flowing material to harden in place to completely seal the external opening of the passage 145. The passage 145 is provided with two depressions 163 (FIG. 6) therein in order to catch any of the flowing cement 161 during the sealing operation to thereby prevent the passage of the cement 161 into the internal part of the circuit breaker housing.

If the circuit breaker trips in too short a time than is desirable, the tool is positioned against the back of the magnet member 117, in the position shown in broken lines in FIG. 5, and the tool is pushed inwardly with a predetermined amount of force to distort the ear or projection 98 in the other direction to thereby increase the amount of stress of the bimetal 97 against the tripping member 79 in the cold position of the circuit breaker. In this case, more bimetal stress must be relieved during a tripping operation so that more thermal reaction of the bimetal will be required in order to effect a thermal tripping operation. It can be understood that this type of calibration must be afiYected when the circuit breaker is in the tripped position so that the trip member 79 is out of the way to permit movement inwardly of the bimetal 97. When the circuit breaker is tested and found to be in proper calibration, the passage 145 is sealed with cement 161 in the same manner hereinbefore described. It can be understood that the metallic frame 25 is fixedly positioned in the housing of the circuit breaker. The frame 25 engages various molded projections in the housing to prevent movement of the frame 25 in the housing. Thus, re-calibration can be effected by operation of the tool 157. It can be understood that the above description applies also to the other circuit breaker mechanism, disposed in the housing part 11, of the duplex or doubletype circuit breaker. It is noted that there is a similar break-otf part 147 on the housing part 11 and it can be understood that a similar passage 145 is provided in the housing part 11 to lead into the internal part of the housing part 11.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from some of the essential features of the invention. It is desired, therefore, that the language of the appended claims be given as reasonably broad an interpretation as is permitted by the prior art.

We claim as our invention:

1. A circuit breaker comprising an insulating housing, a circuit-breaker mechanism supported in said housing, said mechanism comprising a pair of contacts operable between opened and closed positions, a latched trip member releasable to eflFect automatic opening of said contacts, a trip device in an initial position latching said trip member and movable from said initial position to a trip position upon the occurrence of overload current conditions above a predetermined value to release said trip member, said housing having an adjusting-tool passage therein in proximity to said trip device, said housing comprising a tray-shaped compartment part having an open side and cover means covering said open side, said tray-shaped compartment part being molded as an integral part with said passage being formed therein and with a breakoif insulating part molded integral therewith to block off said passage, said compartment part being formed with slot means in proximity to said break-off part for receiving a tool that can be placed in said slot means and levered to a position to break off said breakotf part to thereby open said passage to permit the insertion of an adjusting tool into said housing through said passage to thereby permit adjustment of said trip device.

2. A circuit breaker comprising an insulating housing, a circuit-breaker mechanism supported in said housing, said mechanism comprising a pair of contacts operable between opened and closed positions, a latched trip member releasable to effect automatic opening of said contacts, a trip device in an initial position latching said trip member and movable from said initial position to a trip position upon the occurrence of overload current conditions above a predetermined value to release said trip member, said housing comprising a tray-shaped compartment part having a cavity therein and cover means covering said cavity, said compartment part having a passage therein extending from said cavity and having a break-off part blocking the external end of said passage which break-01f part is molded integral with said compartment part, said circuit breaker mechanism comprising a metallic supporting frame disposed generally along a plane and having a portion thereof bent-over to form a supporting part extending out of said plane, said trip device comprising an elongated bimetal fixedly supported in proximity to one end thereof on said supporting part and extending in a first direction away from said supporting part, said elongated bimetal serving as the sole support of said trip device to thereby support said trip member in said latched position, said passage extending in a direction generally normal to the direction of extension of said bimetal and being in proximity to said trip device, said bimetal and said supporting frame being constructed and arranged such that said supporting frame will distort at said bent-over supporting part when a force is applied to said bimetal in a direction generally normal to the direction of extension of said bimetal by means of a tool that is passed into said housing through said passage to thereby permit adjustment of said trip device.

3. A circuit breaker according to claim 2, said compartment part being formed with an opening therein and a slot opposite said opening in proximity to said breakotf part whereby when a tool is positioned through said opening into said slot and moved with a levering action said breakofi part will break away from said housing to thereby open said passage.

References Cited UNITED STATES PATENTS 3,088,008 4/1963 Gelzheiser 335---45 3,143,627 8/ 1964 Keisel et a1. 2,824,191 2/ 1958 Christensen. 2,573,307 10/ 1951 Casey. 3,275,959 9/1966 Locher 335-42 BERNARD A. GILHEANY, Primary Examiner DEWITT M. MORGAN, Assistant Examiner US. Cl. X.R. 335-45 

